1. Field of the Invention
This invention relates to a process and apparatus for producing blow molded oriented plastic containers which utilizes injection molded parisons which are longitudinally stretch oriented at the blow station prior to final blowing.
2. Description of the Prior Art
There has been longtime commercial acceptance of processes that manufacture injection blow molded articles in a continuous manner wherein a parison is injection formed about a mandrel at a first station, transferred on the mandrel to a second station, where the parison is blown to form the desired article, and then subsequently transferred to a third station for stripping the formed article from the mandrel. Exemplary of such a process is the one described in U.S. Pat. No. 2,853,736.
However, due to the demands of the marketplace, which calls for high strength low weight articles, it has been necessary for the producer to gear his operation to produce biaxially oriented articles. Today, the vast majority of the commercial containers on the market, particularly those made from polyethylene terephthalate, have been made by utilizing preformed cylindrical parisons which are biaxially oriented by stretching the parison and blowing same after the parison has been heat conditioned so that it is at its biaxial orientation temperature. The formation of the parison occurs separately from the heat treat, stretch and blow steps. These machines, unfortunately, are highly complexed, need large floor space and/or require high capital investment.
A commerically available apparatus marketed by Rainville Company Inc. and which functions similar to the apparatus described in U.S. Pat. No. 3,881,854 is characterized in that it is relatively simple in operation and construction, it requires relatively small floor space and it is relatively inexpensive. However, this apparatus as presently marketed does not produce a biaxially oriented article.
There is a need, therefore, for an apparatus and process capable of producing a biaxially oriented article which apparatus and process have the beneficial features of the above-mentioned commercial Rainville apparatus.